NANOMOLAR DETERMINATION OF THE FERROCENE DERIVATIVES USING A RECYCLING ENZYME ELECTRODE - DEVELOPMENT OF A REDOX LABEL IMMUNOASSAY

A recycling bienzyme electrode for determination of nanomolar ferrocen e concentration was developed. The electrode consists of a laccase - g lucose dehydrogenase bienzyme membrane coupled with an oxygen electrod e. Laccase catalyzes the oxidation of ferrocene with oxygen. oxidized ferrocene is an electron acceptor for the reaction of glucose oxidatio n catalyzed by glucose dehydrogenase. The cyclic process of oxidation/ reduction of ferrocene gives substrate recycling. The detection is ach ieved by measuring the decrease in oxygen concentration. In this syste m the detection limit for ferroceneacetic acid was 0.2 nM. Addition of anti-ferrocene-NCS antibodies blocked the electrode response to ferro cene-NCS, while they had no influence on the determination of ferrocen edicarbonic acid and p-aminophenol. The application of these electrode s to immunoassays with ferrocene derivatives as a label is discussed.